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What is the minimum speed a glider can thermal at?
What is the minimum speed a glider can thermal (climb)at, typically, in terms of Vs over a dark field on a warm summer day?
Is it 1.1Vs, 1.2Vs, or 1.3Vs, etc,?

The minimal speed is obviously the stall speed (an aircraft hardly fly when slower), but this is not efficient as you are looking at maximizing climb rate, not minimising speed.

Conceivably, with a strong enough thermal, a pilot could climb even if fully stalled.

The answer depends on several factors:

Bank angle. The minimum speed rises with the inverse of the cosine of the bank angle. A steep bank angle is preferred for best climb because it helps to fly as close to the core of the thermal as possible.
Wing loading. With old designs made from wood and fabric you can get as low as 18 m/s, with modern composite gliders a typical thermalling speed would be 24 m/s with empty and 30 m/s with full water ballast tanks.
Flap setting, static stability and stall behavior. The Schempp-Hirth Discus will happily fly down to a speed of 20 m/s at low bank angle but will develop a high sink rate and very sluggish control response because much of the wing is already stalled. It is better to fly this plane at 23 m/s because then sink speed is lower and control response much zippier.
The maximum load factor the pilot is willing to tolerate. Narrow thermals demand a steep bank angle for best climb speed - see the graph below for an example.

Below please see a graph for resulting climb speed for different bank angles and a cosine-shaped thermal of 215 m diameter. This is not to suggest that thermals will always have this climb speed distribution over their radius, but it is easy to model mathematically. Outside of the thermal's radius the vertical air speed drops to negative values (the rising air needs to be replaced somehow, after all)

The solid black line shows the vertical air speed over the radius of the thermal. The red lines are the load factor with and without water ballast and the blue lines show the angular velocity of the circling motion ($\Omega$, right Y axis). The green lines show the resulting climb speed for both wing loadings. The little DFS Habicht gliders on top illustrate the bank angle for the low wing loading.
The flight speeds at the different radii are:
wing loading    35 kg/m²     50 kg/m²
--------------------------------------
R = 100 m   |   21.44 m/s    27.06 m/s
R =  80 m   |   22.13 m/s    29.56 m/s
R =  60 m   |   24.1  m/s    47.0  m/s
R =  50 m   |   27.38 m/s      –

For this calculation I assumed a typical glider with a maximum lift coefficient of about 1.5 at a Reynolds number of 1,500,000. Both fly at 90% of their maximum lift coefficient, that is $1.1 \cdot \text{v}_\text{S}$ and a lift coefficient of 1.35 for all points.

I do a lot of soaring and you thermal at min sink +/-, which is normally just few knots above stall, around 1.1 Vs.  The slower you can go the better (smaller circle) and sometimes going below min sink is worthwhile if it lets you core the thermal better, but your ability to do this can be limited by the glider's particular stall characteristics and your own flying skills.
On gliders with docile stall behaviour you can pretty much circle on the edge of the stall buffet.  A glider that breaks sharply with not a lot of warning, and wants to roll off, you need to leave more margin lest you enter a spin while above someone else and you might thermal at min sink or a little above.
The Schweizer 1-26 has very docile stall behaviour with a very strong pre-stall buffet that starts well before the stall break, and you can thermal a 1-26 right in the buffet range, shuddering and shaking as you go around.
BTW the best thermals come from lighter brown fields, that are dry.  Moisture in the ground makes it store heat and this tends to move the thermal activity to later in the day, and makes it milder.  Spring time after a very dry winter with little residual snow cover to moisten the earth when it melts will yield boomer conditions on good soaring days.

Thermal flight is generally done at a speed close to minimum sink (which is usually slower than maximum L/D).  This is found by experiment with any given sailplane design, and depends on many factors such as specific airfoil, aspect ratio, spiral stability, and weight (the heavier, the faster you have to fly for minimum sink).
Minimum sink can be roughly calculated from airfoil data, which give lift and induced drag produced for a given speed and angle of attack, but there are so many other variables in the design of a complete airframe that it normally has to be established by testing on the prototype (or the actual article, in the case of a non-production aircraft).  It's typically, however, a small factor above stall, rather than, say, at much higher speed.
The usual sequence of thermal cross country flying is climb in a tight circle within a thermal at minimum sink speed, then when the thermal tops out or, in the absence of pilot oxygen, oxygen altitude is reached, break out and fly toward the next thermal/thermal group/"avenue" toward the destination at "speed to fly" -- which is maximum L/D plus half the reported wind speed.
Rinse and repeat until destination is within a straight glide.
This technique may be modified in ways intended to save time when flying timed or competitive tasks.

Although your answer provides useful information (especially "minimal sink speed") it does not answer the question. You may add how this speed is related to stall speed as the OP specifically asked for comparison of this speed with Vs.

Minimum sink is not a fixed percentage of stall.  It varies with design, mostly with airfoil selection and overall airflow management.

As the OP specifically asks for comparision with stall speed, your comment must be included in your answer (otherwise, I fear it won't answer the question)

@ManuH done.  Seems redundant, to me, but there is is.


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Are there polar plots and airfoil data points available for the RAF4?
Are there polar plots and airfoil data points available for the RAF4?
I understand this is the airfoil used for the horizontal stabilizer of the Zenith 701, which should be similar to a NACA4412 airfoil.

Are you sure of the name RAF4?  I find no mention of it, nevermind its properties, in the usual compendiums of airfoils.  Even the Mighty G finds little after 1918.

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How does distributed propulsion work in a pusher configuration?
How does distributed propulsion work in a pusher configuration?
In a tractor configuration, the wing benefits from a portion of the prop wash flowing over the wing and producing extra lift ( I stand to be corrected).
In a pusher configuration, there is no prop wash flowing over the wing.
So how does distributed propulsion created extra lift and/or thrust in a pusher configuration?

The wings don't benefit all that much.  Look at a small airplane from head on - how much wing is directly behind the prop?
My airplane for example, the prop is 86" diameter. The fuselage is 46" wide - so 20" of wing on either side is behind the prop.
The wing itself is 35'6", or 426", so less than 1/10" is in direct prop airflow.
The prop pulls the plane forward, airflow over/under the wing then creates the lift.

This still doesn't answer the question though.  Also, multiple small shrouded props would increase efficiency greatly. See pic: https://commons.wikimedia.org/wiki/File:Lightning_Strike_unmanned_aerial_vehicle_with_electric_distributed_propulsion_-D60_Symposium-Defense_Advanced_Research_Projects_Agency-_DSC05528.jpg

Air from the prop over the wing doesn't generate the lift that makes and airplane go up - it it did, we could all levitate off the runway.  Air from the prop creates forward speed, the airflow from that speed is what creates lift.  If prop wash was that good at creating lift, then why do the airlines all have their jet engines, which create tons of airflow, blow over the wing to reduce take off distances (assuming they could make wings out of material that could withstand the heat, and that fuel stored in wing tanks wouldn't be negatively affected)?

@Fred, the 2nd link is incomplete and opens a "does not exist" page.  ymb1, the D60 vehicle looks more like a distributed helicopter, altho there might be conventional wing lift created once it gets moving forward.  It does not provide airflow to the front of the wing as an engine in tractor configuration does.

Here is a link to a mid wing distributed propulsion aircraft: https://commons.wikimedia.org/wiki/File:Lightning_Strike_unmanned_aerial_vehicle_with_electric_distributed_propulsion_-D60_Symposium-Defense_Advanced_Research_Projects_Agency-_DSC05528.jpg

@Fred You need to embed and encapsulate the link (click the help link when writing a comment to see how). If you look at your comment, the link is getting broken up because the underscores conflict with the StackExchange software's text formatting parser.

Although the benefit is marginal, the exhaust output of a turbo shaft engine (aka a turboprop engine) is usually vectored to the rear of an airplane.  This does add to the forward thrust of the plane.

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Can one presently register a new flying car in the US as an aircraft and as an automobile?
Can one presently register a flying car in the US as an aircraft and as an automobile?
I understand there is a 1956 Taylor Aircar for sale which is registered and seems to have an automotive license plate.
This may be grandfathered. Source: Aerocarforsale.com

What about a new flying car?
Assuming one can get insurance for both modes, can one presently register one physical flying car as two entities, one as an aircraft, which is registered federally, and one as an automobile, which is registered by state?

I'd think it's not going to pass as street legal, since its wing span does not fit into a lane, perhaps a few other requirements too. Does the source show what license plate it has?

@void_ptr Google the Aerocar.  You park the wings, tail, and propeller at the airport, drive around in the "cabin" with its four wheels.  Come back to the 'port, reconnect, preflight etc. and fly away.  On the road, it's like a compact car (very compact for the 1950s).

@Fred there are a couple companies selling these now, and another in development -- Terrafugia (or whatever they're called now since being sold to a Chinese firm) had gone some way toward FAA and DOT acceptance (the latter the crux for registration as a car) before the after-purchase round of redesigns started.

They are always lousy cars and lousy airplanes.  Like amphibious vehicles.  You use it because you absolutely must have the capability and can live with the crappiness.

@JohnK It appears that no one absolutely had to have this capability.  BTW some amphib IFVs are pretty good vehicles, but of course they aren't boats at all.


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How to calculate how much horsepower is needed to negate wing tip vortices with a wing tip prop?
How to calculate how much horsepower is needed to negate wing tip vortices with a wing tip prop?
I understand 80% of drag is at the wing tips.
Source: Xflaero software notes.
I understand NASA's X-57 boasts a 80% reduction in drag using wing tip propellers rotating contra to the vortice spin direction.
How do you caclulate how much HP is needed to "undo" those vortices?

Please link the source.

Or better yet, quote and link, so we can easily asses the validity.

"Source: Xflaero software notes": What is Xflaero? Did you mean XFLR?


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How to scale the weight of a RC model aircraft?
How to scale the weight of a RC model aircraft?
If the scale of an model aircraft is 1/4, what should the scaled weight be?

Check the chord and speed of the model (Reynolds number) compared to the original.  Models, generally smaller and slower, are usually only a small fraction of the weight of the original.

Does this answer your question?

(coments converted to answer)

If you have a large enough room you can always play around with fluid viscosity. And if you have an extremely large wallet, you can play around with gravity ;)

About 4% to 5% of the original mass.
Scaling laws tell us that area grows with the square and volume with the cube of length. However, this is too simple for two reasons:

Airplanes are not solid but have some hollow space inside. Therefore, their mass grows with something between square and cube.
Wing loading, flight speed and loads grow with increasing size. Therefore, smaller airplanes get away with a lighter structure.

Practical results of the exponent of length to describe mass growth are between 2.2 and 2.3. For a quarter scale model this means that mass will reduce to 0.252.2 = 0.0474 to 0.252.3 = 0.0412 of the original mass.
If design parameters like range (relative to size, of course), payload or maximum load factor change between original and model, the mass will also not strictly follow scaling laws.
In order to know how to scale speed we need to understand which parameters change and which will stay constant. Since we intend to fly the model here on Earth, gravity and air density must stay the same. Gravitational acceleration is length divided by time squared. If length scales linearly, so must time squared. Ergo, time scales with the square root of length. Smaller models fly more slowly but faster relative to length.

What do you mean by it flies faster relative to length? Unfortunately I'm forced to use a longer chord to get at least half the Re. Unfortunately that means the distance between the wing and tail is shorter. The reason I'm asking about scaled weight is to get a scaled Ixyz that will resemble the flight characteristics of the full scale aircraft as much as possible.

@Fred Speed is distance over time. Now scale that distance with your length change and compare actual speed with that length-scaled speed.

This is an example of the square-cube law.
The square-cube law states that for three-dimensional objects, scaling linear dimensions results in the surface area varying proportionally to the square of the change in linear dimensions, and the volume varying proportionally to the cube of the linear dimensions.
So, for a model aircraft 1/4 the size of the original, its surface area should be 1/16th that of the original, and its volume (and mass) should be 1/64th that of the original, 16 being 4 squared and 64 being 4 cubed.
However, the support members of a 1/4 scale model aircraft need not be as strong as that of the full sized model due to the same square-cube law due to their only needing to support 1/64th of the original mass yet being 1/4 the size.  That's why mice and insects seem to have sticklike limbs compared to elephants.
So, a 1/4 scale model would likely be less than 1/64th of the weight, or might carry a significantly larger payload.

Peter's answer shows how for this application, the square-cube law is a good approximation but we can do better.

What is your basic purpose for trying to scale the weight? Wouldn't the lightest possible model you can possibly build always fly best? After all, you can always fly it faster than the actual minimum stall speed, if it suits your purposes for looking more scale-like.
Keep in mind too that there are two different contradictory issues as to what sort of flying speed looks the most "scale like". On the one hand, we can think of the time needed to cover one fuselage-length and scale that to match the real thing. That will always result in slower speeds than you might tend to expect. On, the other hand we can think of the degrees of turn per second generated at a given bank angle, say 45 degrees. To match that to the original, you'll have to fly fully as fast as the original.
So if you slow down enough to satisfy the first criteria, your turn rate for any given bank angle will look way too fast. So the best airspeed to fly for the most "scale-like" appearance is somewhat ambiguous.
(Yet another alternative would be to fly at an airspeed that scales the turn radius at any given bank angle to the full-scale airplane.)
But since a light model can always fly faster than its stall speed, but a heavier model cannot fly slower than its stall speed, it would seem that there would be no advantage to building heavy rather than light, as far as presenting a scale-light appearance in flight is concerned.  So we're back to asking, what is your basic purpose behind trying to "scale" the weight to match the original in some way?
(Some of the answers already posted appear to address the likely weight of the model, rather than the ideal weight of the model.)
The basic answer to your question appears to be "it's best to build the model as light as you reasonably can."

Lightest isn't always "best," even full scale.  For instance, sailplanes both big and small carry ballast.  But apart from that, they are indeed built as light as can be.

@CamilleGoudeseune -- well, sailplane flight dynamics are rather different than powered  airplane flight dynamics, as you know doubt know.  But I'm sure there is some weight below which the flight just wouldn't look quite right-- hard to articulate exactly why though.

@CamilleGoudeseune -- yeah you are probably on to something, in that you probably want the power-off or power-idle gliding speed that yields the best glide angle, not to be unreasonably low, for scale-looking landing approaches.  For reasons noted in the answer, it would seem to be hard to pick one single ideal speed and thus one single particular ideal weight, to make said power-off or power-idle approaches look as scale-like as possible.  It depends on what criteria you are most interested in.


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How to determine dihedral angle?
How to determine dihedral angle for a high
wing ga aircraft with 12' wing span?
While there are formulas for determining
size of the vertical and
horizontal tails, I have yet to find a simple
formula for determining the dihedral angle.
According to the aircraft design book
"Flying on your own Wings" by Chris Heinz,
the designwr of such aircraft as the
CH701 STOL aircraft, the author suggests
using 3 degrees for low wing, and 6 degrees
for low wing, but I would assume this is
just valid for traditional ga wingspans
of 25' to 30' and not short wings spans such as 12',

Did you mean to write "using 3 degrees for low wing, and 6 degrees for low wing", or something else?

I bet "using 3 degrees for high wing, and 6 degrees for low wing" was intended.

Are you designing a (possibly hypothetical) plane, or trying to measure ("determine"?) the dihedral angle of an exisiting plane?

You have to decide how much counter roll response due to sideslip (roll/yaw couple) you want. You get positive dihedral effect with a high wing with zero geometric dihedral, just milder than if you add geometric dihedral. Lots of high wing airplanes have straight across wings. The Wittman Tailwind has a short span, only about 20ft +/-, with zero geometric dihedral, and its roll stability is adequate, being intended as a fast cross country airplane, tho some builders will add a degree or two of geometric dihedral to enhance it.

“High-wing airplanes often have little or no dihedral [or even anhedral], whereas many low-wing airplanes have geometric dihedral angles of as much as 10 deg.”  Airplane Flight Dynamics and Automatic Flight Controls, by Jan Roskam.
First, I'm assuming your design requirements for maintainability, visibility, manufacturability, propulsion system integration, or landing gear integration do not factor into your choice of dihedral. Therefore, this answer will focus on the primary aerodynamic stability & control effect of dihedral, which is its effect on roll due to the sideslip angle, Beta (ClB).
It's important to recognize some other key geometric parameters (in addition to the wing position relative to the fuselage) that effect ClB, especially wing sweep, wing aspect ratio, and details of the vertical tail geometry.
You want the entire configuration’s ClB to be < 0 for static stability. However, if it’s too negative (i.e., too laterally stable), the Dutch roll mode is aggravated. Also, it could result in slow rates for commanded rolls.
All things being equal, more wing dihedral tends to decrease ClB, therefore adding lateral stability.
For conceptual design on a traditional configuration, I would simply choose zero dihedral from a purely aero/S&C perspective. Beyond conceptual design, some low-order computational aerodynamics tools could provide a decent check that you’re in the ballpark*. If/when getting more serious in terms of tooling, capital and/or life & limb at stake, wind tunnel test and 6-DoF simulation will substantially burn down risks.
Fundamentals of Aircraft and Airship Design, by Nicolai & Carichner is another good reference
*Shoot for ballpark -0.1/rad for derivative of rolling moment coefficient wrt sideslip angle

Dihedral angle is measured as a positive (or negative) angle to a horizontal plane running perpendicular to the aircraft vertical centerline, viewed head on.
Since you are working with a 12" model, there is plenty of room for experimentation!  Glide you model in a cross-wind, and see what it does.
The old high wing/low wing saws for full scale aircraft do apply to models but it is important to know where your vertical Center of Gravity is.
If your model turns into the cross-wind, the dihedral effect (to a cross-wind) is not too strong, if it turns away and tries to fly downwind, the there is too much dihedral.
Dihedral effect can be reduced by raising the center of gravity, reducing dihedral, reducing sweep, or by adding side area below the vertical CG.
Fancy spats on fixed landing gear would work well to do this (and possibly also reduce drag).  Lowering the vertical stabilizer a bit would also help.

I think the O.P. is in fact asking about a 12 foot wingspan, not a 12 inch wingspan. That may affect the "room for experimentation" available.

I believe the concern is: do the angles scale.  They do, and other factors are involved in good crosswind performance.  Gliding tests remain essential, and scale models could be built.  There is also a wealth of knowledge going back many years for mono and biplane designs.


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What is the ultraviolet signature, if any, of aircraft and jet engines?
The Wikipedia article on the FIM-92 B variant of the Stinger Missile says:

In this version, the infrared seeker head was replaced by a combined IR/UV seeker that utilized rosette scanning. This resulted in achieving significantly higher resistance to enemy countermeasures (Flares) and natural disturbances. Production ran from 1981 to 1987, a total of 600 missiles were produced.

I'm assuming "IR/UV" means "infrared/ultraviolet."
Do aircraft (or jet engines) really have a strong ultraviolet signature? If so, how is it formed? Is it only evident at high airspeeds?
(Also, what on Earth could it be talking about by "natural disturbances"?)

In addition of the black body UV radiation which is very limited, UV are produced in the engine plume (especially afterburners) by fluorescence, and UV trom the Sun are reflected by the aircraft. An UV sensor sees all of them and try to contrast the aircraft UV and the background which is full of UV from the Sun. On the other hand flares do not produce, reflect or transmit UV. While IR analysis may fail to contrast targets and flares, UV analysis can distinguish between them. IR and UV sensors are usually combined in the analysis.

Your assumption is correct - it is indeed about infrared (wavelength between 750 nm and 10,000 nm) and ultraviolet (wavelength between 100 nm and 400 nm) radiation. The sensor detected two specific wavelengths, one from each range.
Every body emits an electromagnetic radiation, both as thermal radiation and from reflecting other radiation sources. Thermal radiation has an intensity distribution which shifts to shorter wavelengths with temperature. By comparing the intensity of the IR and UV parts of this radiation, the sensor can much better distinguish between radiation sources of different temperature. Flares are normally hotter than engine exhausts, so by detecting an excess of UV radiation, the sensor can distinguish between flares and exhaust pipes.

"Wiens law" by 4C - Own work, based on JPG version. Licensed under CC BY-SA 3.0 via Commons.
Natural disturbances means reflected sunlight off a polished aircraft surface or canopy, or off lakes or windows on the ground. Even after filtering by the upper atmosphere, sunlight will contain much more UV radiation than your average exhaust pipe, and glares were a big distraction to early thermal seekers. Sunlight would correspond to the green line in the diagram above, while the exhaust would be even below the dark red line.
Note that the absolute intensity also goes up with temperature, but would not help in identifying the temperature of a target if only one wavelength is observed. A more distant, hotter target would cause the same intensity than a colder, closer one. By sensing two wavelengths, the sensor could much better tell an exhaust pipe from other heat sources.
To answer the question directly: The UV signature of the aircraft itself is practically zero except for the reflection of the UV part of sunlight, and the active UV emission of a jet engine is extremely low and concentrated around its exhaust when seen from behind. Lighting the afterburner will increase the UV radiation, but it will still be much less relative to the IR radiation that that of, say, burning magnesium.

If I'm reading this correctly, then IR/UV missiles will not work at night?

@DrZ214: Why would you think so? At night you have no distraction from sunlight, so an IR seeker has even less trouble to find its target. The radiation from the hot exhaust pipe and flares would still be the same, so the seeker will work at night as it does during daylight.

I'm talking about the UV part. The UV signature of the aircraft itself is practically zero except for the reflection of the UV part of sunlight, and the active UV emission of a jet engine is extremely low So it sounds like the UV tracking won't work at night?

@DrZ214: Tracking is still done by IR, and UV is used to classify the IR source. No sun reflections just means less false positives that need to be weeded out. IR tracking at night is easier. Again, at night you have no distraction from sunlight, so an IR seeker has even less trouble to find its target.

I'm reading this as - "sources which have a significant UV component are ignored, as they are unlikely to be the engines"

What is the ultraviolet signature, if any, of aircraft and jet
  engines?

The exhaust plume of the jet engine that has radiation which flickers within the Ultraviolet Range and the ultraviolet light radiation that exists as a result of a pressure wave on the tip or leading edge of the aircraft  that is moving fast enough to create a sonic pressure wave. Several different constituents of a jet engine – accretion flow; stellar magnetosphere; winds and inner parts of the accretion disk radiate in the Ultraviolet spectrum.

I'm assuming "IR/UV" means "infrared/ultraviolet."

Correct

Also, what on Earth could it be talking about by "natural
  disturbances"?

In this context, what it means is that Infra-Red (IR) is the main method of tracking the target. Ultraviolet(UV) is used in addition to discriminate the target from flares and "natural disturbances" like direct sunlight or sunlight reflecting from clouds as they usually have totally different amount of UV radiation compared to the target. Basically they are referring to the Proportional Guidance system of the Stinger MANPAD. Since the primary job  of MANPADS like Stinger is to  stay locked on, the  heat seekers’ fields of view are usually small to prevent distraction from competing sources.Seeker optics magnify IR/UV signatures emitted by distant aircraft,keeping track of the target aircraft is another matter altogether

"Ultraviolet(UV) is used in addition to discriminate the target from flares" does this means that there is no UV decoys/flares ?

@ManuH, no, it means that most decoys/flares produce too much UV and the seeker can filter them out based on that.

@JanHudec That seems odd. If it makes too much UV, then it should be able to blind the sensor (prevent it from seeing anything else such as the real target).

@DrZ214, not too much as to blind the sensor (that would take quite a lot of energy). Just the ratio of brightness in UV and IR is much higher.

You're correct that IR/UV means Infra red/Ultra Violet.
In general, the aircraft (or its exhaust) does not have any appreciable UV emission.
MANPADS such as Stinger using a IR detector can be confused by launching flares that have the same (or similar) IR signature.
The reason the UV sensor was added was that that it can be used to discriminate the target by detecting the 'UV shadows' cast by an aircraft in a background sky radiance of atmospherically scattered solar UV. These will be different for the actual aircraft and the flares.
Some Soviet missiles achieved the same effect by using IR sensors in two different wavelengths, while most modern missiles have sensors of sufficiently high resolution to discriminate the target.

If this is true, then IR/UV missiles will not work at night?

@DrZ214 - they work fine at night. They don't rely on IR/UV reflected off the a/c---they rely on IR/UV emitted by the target a/c.

Contrary to the suggestions in replies to this question the UV seeker of the FIM-92 Stinger looks for the "shadow" created by an aircraft against the relatively bright UV background of the sky.  The aiming and arming procedure of an FIM-92 with a dual-frequency seeker involves, amongst other things, aiming the seeker at a patch of empty sky for calibration purposes.
At night one imagines it reverts to the more basic modes alluded to above.
UV seeking mode mentioned here: https://bit.ly/2Hm59w5
Still working on where I discovered the "point seeker at empty sky" calibration procedure.

http://www.armyrecognition.com/united_states_american_missile_system_vehicle_uk/stinger_fim-92_fim-92a_man_portable_air_defense_missile_system_manpads_technical_data_sheet_picture.html

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Was the Shuttle Orbiter in contact with air traffic control during its descent & landing?
The Shuttle Orbiter crew were obviously in contact with ground control in Houston during their landing, but were they also in contact with any air traffic control, especially once they reached US airspace? Was US ATC involved in the landing in any way other than keeping other traffic out of their way?

Related, STS-65 - Video from the cockpit with audio: Launch, re-entry, landing, see also Nasa Facts - Landing the Space Shuttle Orbiter.

Also related: https://space.stackexchange.com/questions/35805/has-any-spacecraft-ever-had-the-ability-to-directly-communicate-with-civilian-ai

Well, sort of. The Kennedy Space Center, where the shuttle operations were conducted, has an ATC. but then, the show was run by NASA, not FAA.
The shuttle operations were coordinated through the Aerospace Control Officer (ACO) at the Air Force 45 th Space Wing’s Eastern Range (it used a military TACAN). FAA was informed of the shuttle landing and nothing else. NASA simply cleared the airspace for a 30 mile radius around the intended landing site to prevent collisions.
In the trajectory of the shuttle landing, FAA issued a NOTAM called 'Space Shuttle Landing Operations Advisory' to warn the users that 25 miles to either side of the nominal reentry trajectory is potentially vulnerable to debris, but the airspace is not closed, like this example:

FDC 9/1945 (A0856/09) - ...SPACE SHUTTLE LANDING OPERATIONS ADVISORY...
  EFFECTIVE 0911271848 UTC UNTIL 0911271923 UTC SPACE SHUTTLE
  LANDING OPERATIONS 25 NM EITHER SIDE OF THE LINE BETWEEN
  2743S/17214W 0411N/16214W 2925N/13455W 3440N/11828W 3457N/11745W
  FROM SURFACE TO UNLIMITED. WIE UNTIL UFN. CREATED: 25 NOV 21:11 2009

For these actions, Special Use Airspace was activated. The ACO coordinates these actions with the FAA’s ARTCC (Air Route Traffic Control Center) in Miami, Florida

How does ATC fit in the control system? Control was first from KSC launch control center. After the STS cleared the pad tower, control was handed over to a flight control room of the Mission Control Center in Houston. To my knowledge only the Capcom could talk to the crew from Houston.

Pretty sure the K.I.S.S. (Keep It Simple for the Spacemen) principle applies, and NASA owns the airspace.  Really, what is Center going to tell the shuttle? "Go around?" Nah. Welcome back? Probably, but that's more a distraction than anything.
ATC would be involved in keeping the airspace clear of other traffic, certainly.

It should also be noted that during at least part of the decent the Shuttle was incapable of radio transmissions. This was a problem common to all space craft reentering the atmosphere. The problem was apparently solved latter in the space program with the TDRS communication platform but the early shuttles were subject to a black out that lasted as long as 30 minutes. Since the US does not have an official definition of the start of space (although they use the generally accepted Karman line) its hard to even say where airspace ends and space begins. There is technically no upper bound to Class E airspace here in the US, the official wording is

§71.71   Class E airspace. Class E Airspace consists of:
(a) The airspace of the United States, including that airspace
overlying the waters within 12 nautical miles of the coast of the 48
contiguous states and Alaska, extending upward from 14,500 feet MSL up
to, but not including 18,000 feet MSL, and the airspace above FL600

Note: you dont need to contact ATC to enter class E but they will need to pass through the class A at some point.
Also of some interest, you need a valid FAA pilots license with an instrument rating to fly a reentry vehicle.

(c) A pilot and a remote operator must—
(1) Possess and carry an FAA pilot certificate with an instrument rating.

All re-enty and launch paths must be filed with the FAA as well (I assume this is to they can issue the TFR)

§431.79   Reusable launch vehicle mission reporting requirements.
(a) Not less than 60 days before each RLV mission conducted under a
license, a licensee shall provide the FAA with the following
information:
(1) Payload information in accordance with 14 CFR §415.59 of this
chapter and §431.57; and
(2) Flight information, including the vehicle, launch site, planned
launch and reentry flight path, and intended landing sites including
contingency abort sites.
(3) Launch or reentry waivers, approved or pending, from a federal
Federal range for at which the launch or reentry will take place, that
are unique and may affect public safety.
(b) Not later than 15 days before each licensed RLV mission, a
licensee must notify the FAA, in writing, of the time and date of the
intended launch and reentry or other landing on Earth of the RLV and
may utilize the FAA/U.S. Space Command Launch Notification Form,
contained in part 415, Appendix A, of this subchapter for doing so.
(c) A licensee must report a launch accident, launch incident, reentry
accident, reentry incident, or other mishap immediately to the FAA
Washington Operations Center and provide a written preliminary report
in the event of a launch accident, launch incident, reentry accident,
or reentry incident, in accordance with the mishap investigation and
emergency response plan submitted as part of its license application
under §431.45.

Directly to the point the FAA does require a communications plan but seems to specify more what needs to be communicated than mandating they are involved.

§431.41   Communications plan.
(a) An applicant shall submit a plan
providing vehicle safety operations personnel communications
procedures during the mission. Procedures for effective issuance and
communication of safety-critical information during the mission shall
include hold/resume, go/no go, contingency abort, if any, and
emergency abort commands by vehicle safety operations personnel. The
communications plan shall describe the authority of vehicle safety
operations personnel, by individual or position title, to issue these
commands. The communications plan shall ensure that—
(1) Communication networks are assigned so that personnel identified
under this section have direct access to real-time, safety-critical
information required for making decisions and issuing commands;
(2) Personnel identified under this section monitor a common intercom
channel for safety-critical communications during launch and reentry;
(3) A protocol is established for utilizing defined radio
communications terminology; and
(4) Communications affecting the safety of the mission are recorded in
a manner that accurately reflects communications made on individual
channels, synchronized time coding, and sequence of communications.
(b) An applicant shall submit procedures to ensure that licensee and
reentry site personnel, if any, receive a copy of the communications
plan required by this section and that the reentry site operator, if
any, concurs with the communications plan.

You can find all the FAA regs on space flight here.

If the pilot of the shuttle is in the US military there is surely no requirement for them to hold an FAA license

That is incorrect, NASA is its own organization. While they may hold the hours NASA may still require them to get an FAA license. Any military pilot that leaves the military (even with thousands of hours of stick time) still needs to get an FAA issued license to fly non military.

@Dave The FAA spaceflight regulations you're quoting do not apply to spaceflight operations carried out by the US government for the US government. NASA is not generally required to obey them on government-operated spaceflights; that includes the requirement that the pilot of a reentry vehicle have an FAA license with instrument rating. The FAA has limited authority in general over noncommercial government operations.

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


text:
Is there a fuel injector cleaner additive available?
I have not seen any additives (such as those used in automobiles) to clean and maintain fuel injectors in aviation engines.   Is there a reason for that such as the use of lead in 100LL or something else?   The fuel injectors will eventually constrict or clog as the avgas leaves residual deposits.
Is there some technical reason or is it just that no one has gone through the certification process or at least (like AVBlend or CamGuard) received the "will do no harm" approval from the FAA?
Removing, cleaning, reinstalling fuel injectors is not only expensive but you also risk damaging them and if you have the GAMI injectors you can have quite a bill coming at you.

Fuel injectors in GA piston engines are actually fixed nozzles, so short of fuel contamination, are not so easy to clog,since the only thing that can  be deposited with clean fuel is the blue dye in the avgas.
In 8 years maintaining a fleet of 6 to 8 injected Continental engines, running 200-700 hours / year, I did not see a fuel-deposit blocked nozzle. Deposits did change the flow rate enough for us to routinely clean them ultrasonically (our pilots were cruising lean of peak, and would start complaining), but removing, cleaning and reinstalling the injector nozzles was a routine, straightforward and scheduled event in my experience.
With position tuned nozzles, as current Continental ones are, you need to be careful to get them back to their correct position, just like GAMI ones, but it's not rocket engineering. The torques for installation are in the manuals, and they are not the most challenging item to work on (one b-nut and one pipe thread per nozzle) on the average GA engine. There's no need for special additives.

While this is a great answer to a slightly different question, it does not answer this question.

I'm not aware of any FAA-approved (or FAA-accepted) products for on-engine fuel injector cleaning. If your injectors are blocking due to lead deposits a tricresyl phosphate additive may help improve lead scavenging and prevent the problem, but it's probably not going to clean a clogged injector. (TCP is also pretty nasty stuff – leaning your engine more aggressively can often accomplish the same thing without the chemicals.)
Frankly 100LL is a pretty darn good solvent: it even dissolves that blue dye they put in it which nothing else ever seems to budge. If your injectors are blocked due to contamination that 100LL won't dissolve having your mechanic take them off and bench-clean them is probably a good idea (as Thomas pointed out this isn't rocket surgery - any competent mechanic should be able to do it without damaging anything).

As far as other "pour it into the gas" cleaning additive, as with many things There's an Advisory Circular that covers this (AC 20-24D) - at least to some extent: That Advisory Circular deals with fuel specifications for type certification of aircraft/engines/APUs, but it contains this interesting nugget:

(1) Fuel additives that are incorporated into ASTM, governmental or military specification, or other industry-based consensus organization specification, are considered to be identified in sufficient detail to be accepted by the FAA under existing operating limitations on TCs, amended TCs, STCs, or ASTCs, provided there are no changes to those operating limitations.

So if you can show that the injector-cleaner chemical you want to use is an approved additive according to ASTM D910 (the standard that governs 100LL avgas), your use of the additive is in accordance with the specification ("not more than X% or Yppm"), and the additive is not contraindicated by the manufacturer (of the engine, airframe, or any components) you should theoretically be OK to use it.
Navigating that legal morass is something you probably don't want to do though: The risks of getting it wrong are not just paperwork-related: some additives can damage your fuel system, or even lead to an engine failure.
A bench cleaning of your injectors is probably the easier and safer option.

I believe that is the circular, which you quoted, that allowed AVBlend and CamGuard to sell their oil additives.    My question was not to the extent to clean a clogged injector but as a preventative measure to avoid future clogging and a possible scrub of a mission to have the injectors serviced.   Thanks.

@TBFlyer I'm not sure if that AC was the totality of the justification for AvBlend & CamGuard - I believe they went through some additional processes - but I'd bet money they referenced it :) Re: preventing injector clogs, if that's your goal I personally think aggressive leaning is your best bet to avoid lead deposit clogs, and following that using fuel additives containing TCP. I'd only consider the latter if you have a repeat problem you can trace to lead deposits on the injector though.

Keep fuel injector clean by using fuel injector cleaners isn't a bad choice at all. I have been using them for years. Try Chevron, Lucas or BK44 to see different between before and after.


text:
Problem with right crosswind landing but not left
The prevailing winds where I'm training are almost always straight down the runway or from the left. I have no problem landing on (and staying on) centerline in either case.
However, when the crosswind is from the right, I tend to land on the centerline and then skip leftward.
I thought it was just me being inconsistent about my crosswind correction. However, during a recent lesson with wind 090, I was nailing every landing on 18, but when tower turned the airport around, I botched every landing on 36, so that seems to rule out coincidentally having a bad day every time there happens to be a right crosswind.
My CFI can't explain why I'm only having a problem with one side, much less how to fix it, and seems to be blowing it off since (now that the winds are back to normal) the problem has "gone away" again, but I'm not satisfied with that.
What could be causing this, and how do I practice for right crosswinds specifically when they are relatively rare here?

Are there no other airports in your vicinity with a different runway orientation?

@Sanchises With such consistent winds, all the runways (at least at GA airports) are lined up the same way. Few fields have even two, and those that do are parallels.

Can you try flying from the other seat?

What type of aircraft?

I would guess you're in a single-engine plane and the direction of rotation of the engine is the major factor in this.

@A.I.Breveleri I'll see if the CFI will let me try that to see if it reverses the problem; good idea!

@Davidw All C172 so far.

@HotLicks That's what I was thinking as well.

In my opinion it's because of your left of centerline vantage point and the sight picture burned into your brain by the always left side crosswind aspect, and in your particular case the transition to an opposite aspect is confusing your eye/brain/hands-feet processing more than other people. Everybody has their learning quirks.
The sight picture you are used to from your seating position, which includes the azimuth aspect (heading relative to center line) and bank angle from side slip, is a much bigger deal than a lot of people think.  When pilots start flight instructor training, one of the first airborne activities is learning to fly a trainer from the right side.  Some adjust right away, and for some it's like learning to land all over again.  In your case it seems you are having a similar problem with the left crab/right crab change in sight picture from the left side.
You just need to practice right side crosswind landings until that sight picture starts to sink in and responses become automated, and then you will wonder what all the fuss is about.
I second Carlo's suggestion to use a home computer flight sim for this sort of thing, which are perfect for this sort of "sight picture" learning (use Track-IR as well because this provides much more realistic sight picture movement).  Should help a lot.  But, be careful that when you practice things at home you are practicing correct procedures, not reinforcing wrong ones; that's the one big pitfall of using home sims for practice/proficiency.

It's very likely the difference in seat height when slipping left versus right.   Since the pilot will be higher from the ground when slipping because of a right crosswind, it will cause a later flare (assuming that he is flying from the left seat) if not corrected for, and the late flare can easily cause a skip/bounce.  As you said, it just takes practice to learn the new sight picture.

@Lnafziger I think that detail explains why this answer is (most) correct. Thanks!

But a slip while landing is only a few degrees of bank so I'm not sure that is as big a factor as just the left/right orientation.  When I first drove right hand drive in UK I had no problem staying on the correct side of the road, but I had a terrible time trying to stop driving left wheel on the shoulder, from subconsciously trying to restore the left side of the lane sight picture I was used to, with my view point on the right side of the car.  In any case, it will take care of itself eventually.

@johnk It's more than you may think, especially in a strong crosswind.  Watch a light trainer landing on a windy day and see how high the opposite wheel is off the ground when the lower one touches down.  Now, double that since it's the other wheel which is normally up.  When you are flaring and trying to touch down smoothly, even a couple of feet can make a big difference.  As far as centerline, most people simply land off to one side when learning to fly from the other seat (which isn't even a factor in this case), and learning to fly with the opposite hand is the more difficult aspect.

@Lnafziger on reflection I agree with your comment and have added a bit to the post to reflect that.  Thanks.

Good answers, but one thing not mentioned is the fact that people are rarely completely ambidextrous.  (I would guess that you are probably right handed, is this correct?)  Because of this, we have a natural tendency to be more comfortable doing things in one direction over another.  I have noticed this in my own skiing, and from instructing others; right handed people tend to be more comfortable turning left for some reason.
Being right handed I also tend to be more comfortable when the crosswind is from the left.  Couple this with the fact that you have had much more practice with left crosswinds and it's no wonder you are less comfortable when wind is from the right.  My advice is the same though, seek out opportunities to practice!

So, this is actually very likely part of the problem too, and likely due to the fact that most of his training was done from the left seat, using his left land to control the yoke and the right hand to control the power.  When you move to the right seat, the roles  of the hands reverse, and the muscle memory which has been learned now has to learned again using the new muscles!

Carlo already mentioned the most probable cause to your drift to the left: aiming point being too close in front of you, I've dug up a couple more points from the archives of my mind for you to check :

The footwork is not symmetrical in left and right crosswind landings. This is because of the prop slipstream. As you've kicked the plane in alignment with the runway before touchdown, you have propably just retarded the engine at idle or are about to do that. You'll compensate for prop slipstream dissapearing by easing off right rudder ever so slightly. Now, depending on which side the crosswind is blowing from, the feeling should be different. You might be unconsciously trying to replicate the feeling in your feet to be the same.
I'm guessing you are flying a side by side cocpit, yes? your perspective is not the same on different crosswind directions. The difference in point of view is very small, about two feet, but for a beginner that's plenty enough to fool one's brain. You've mastered the left crosswind, you'll have to get used to the fact that stuff looks slightly different from where you sit, and the visual cues are a tad bit different.

I think you are gently sliding sideways during touchdown when you land in right crosswind. You manage to plant the plane on the centerline, but inertia drags you to the left.
Best fix for both points is to first and foremost do what Carlo suggested: aim at the end of the runway. You're not driving a car, so what's a 100 meters ahead of you is secondary, don't worry about it. Second: create a mental picture for yourself of what you must do to keep the plane on the centerline. Fly (or actually land) ahead of the plane.
And last but not least: don't worry about it, practise and one day it'll all just click into place inside you're head. After that, it's good for life as long as you keep flying.
caveat: It's been a while for me, but I worked it out, IIRC with the aforementioned cures

I have no problem keeping the nose pointed straight down the runway; it's just that in a right crosswind, the plane slides sideways toward the left side, which makes the tires skip. If the plane were turning, I'd think they wouldn't skip.

If the tires are skipping and you are sliding to the left just after touchdown, it means you have lateral momentum at the time of the touchdown @StephenS : you are not flying parallel to the centerline. You need more bank angle towards the wind. You may be trying to make the crosswind landings look like mirror images from each other, the trick is to realize they are not mirror images, not visually and not from the steering point of view.

Most likely this is inconsistency with your crosswind techniques in the round-out.   Remember: use rudder pressure to point the nose at the far end of the runway, and aileron pressure to hold the aircraft on the centerline of the runway.  Just how much pressure it takes is whatever is required to achieve and maintain these metrics.  Also be mindful that you were not relaxing control pressures once you touch down. Remember to continue flying the airplane until you slow it to taxi speeds.
As additional practice, you can do it in a simulator like Prepar3-D.  Set the local winds to whatever you want. This is a good way to practice your technique in moderate to extreme crosswinds, which would otherwise be hazardous to do in the actual airplane. That’s how I got to good at crosswind techniques.

This doesn't seem to address the central point of right vs left. It would be a good answer if I had problems with both.

No what it means is the student is probably doing this correctly when landing in a left crosswind but not doing so in a right crosswind.  This does happen from time to time.  The CFI should demonstrate to him the proper sight picture or make the needed corrections just prior to touchdown to show the student what he's doing wrong and how to correct it.

Long back  I used to fly single engine piston aircraft which had large keel area making it very susceptible to crosswinds.  I observed that whenever the winds were from right I had no problem in giving right aileron (right wing low) and left rudder and land on CL with nose straight. Strangely if the winds were from left some how I was just not comfortable in putting on bank to left (sitting on the left seat). I analysed that there was some sort of apprehension (may be intrinsic or subconscious) in putting myself down towards left. I always found it difficult to put on the required bank to the left. And it was more of some sort of unexplained fear or apprehension. Now I fly four engine big jets and whenever faced with significant cross winds from left I remind myself to look all along the the entire length of the Centre line during the last stages of the flight. Looking at the correct place ensures controls are moved in the correct sense and proportion. I hope it helps somehow. And I am a right hander.


text:
Could I issue clearances at a private airstrip without being a controller?
Hypothetically, if I owned a private airstrip on my property, with all the necessary permissions to do so, and I only want certain aircraft landing there, would I be allowed to issue takeoff and landing clearances even though I am not an air traffic controller?

Where in the world?

This question and related answers may be of some help: https://aviation.stackexchange.com/questions/3292/can-an-airport-without-an-faa-controlled-tower-have-their-own-tower-and-controll?rq=1

This is probably similar to what happens on the advisory frequency at untowered airports, you can issue "advisory" information but it is still up to the pilot to determine the traffic and best course of action to land.

Related: you can't give clearances, but you could provide a UNICOM-like service

There seems to be many opinions and no clear answer on this interesting question.

@Fattie there absolutely is a clear answer: No.

I second J Hougaard. The word "clearance" has a specific meaning with legal ramifications. A pilot could call you and ask permission to land on your strip, but beyond that you can't be giving vectors or clearances. You've got to be licensed and have proper equipment for that.

OP, would "permissions," "instructions," or "approvals" fit your use of "clearances"?

@Pondlife, clearances can be given if the private airstrip had a NFCT.  I can find no regulation preventing that.  Can you provide authoritative cites of regulations which would prevent that?

@mongo I have no idea, but I don't see why not. I've never heard of a private (civilian) field with it's own tower but maybe there's one out there. I understood the question as a more informal situation, e.g. a grass strip on a farm. But I could be wrong, the OP didn't give much detail.

Was the original intent of the question to ask "May I legally control the flow of traffic in and out of a private field"?  As far as I know there is no law against any toddler getting on the radio and issuing clearances to their heart's content.  At least in the case of a private field where there is no requirement for a clearance to be obtained.  I  may be mistaken there though.

In the past when airport owners want to control traffic flow, they file a NOTAM that the airport is closed, and contact xxx at 123456789 for exceptions. Then for the takeoff, the airport manager would issue a verbal "the airport is open for N1234 to depart" and then close the airport.  This could be done on the unicom, in person, via telephone or however one wanted to.  This happens at some private and corporate strips.  It is actually more common in the northern parts of Canada, where there are fields operated by mining companies. In those cases, authorized aircraft come and go, and the field appears as a restricted use field. (Often they are not even charted, even though they may have VOR-DME on the field.)
So in summary, you have at least two paths to take: 1. NOTAM the field closed, or 2. Restrict the use

If you really want to play controller, you could install a private tower, or Non-Federal Contract Tower (NFCT), but then there are a bunch of rules to follow, and I believe your tower controllers would essentially have to be FAA trained. But I am not up on those regs, and they may have changed since I was more fresh on them. Here is a sample NFCT set up for an event.
Specifically, the FAA permits NFCTs, whereby an agency or entity that wishes a towered airport which does not meet federal criteria, or is otherwise unable to get an FAA Contract Tower (FCT), may operate a control tower.
Technically, this satisfies the OP criteria for issuing "clearances" but perhaps with a little more red tape than he might be interested in.
AC 90-93B states in part: "There are no comprehensive set of federal rules governing the operation of NFCTs." The Advisory Circular goes on to make recommendations for procedures, policy, training and equipment.
In summary, if you want to install a tower at your private field, you can do so.  Good luck getting insurance.  Make sure you follow FCC Part 87 for your radio licenses.  Spend some time working with your center, and regional approach facilities.

OP wanted to "issue takeoff and landing clearances" at private field. Examining the constructive meaning of that, it means that he wants to regulate flow into and out of his field. The three concepts presented here, NOTAM, Restricted Airport and NFCT, each allow the OP to effectively accomplish flow control to and from his field. All three methods are common practices, and recognized by the FAA. Since the OP appears to not be well versed in FAA terminology, the word "clearances" should be liberally construed to the meaning of controlling airport flow. He did not talk about routing, altitude et

Perhaps "instructions" or "approvals" might be more appropriate than "clearances."

you are correct in that I am not well versed in terminology, because I am attempting to learn still. I just thought of this situation and wondered how regulations address this (very) niche case. To answer your question, yes, instructions or approvals would be more appropriate.

NO!
An uncontrolled field is just that - uncontrolled. No pilot will accept a clearance in uncontrolled airspace in the first place. Consider the legal consequences if two aircraft were to collide as a result of a "clearance" issued by you. Since the aircraft are in uncontrolled airspace, it is the responsibility of the pilots to make sure they do not get too close. However,  if you got on the radio and started issuing "clearances", you might trick pilots into thinking that you are in control. If something bad happens, you should not expect to just walk away from it.
Besides, what makes you think you are qualified to provide air traffic control? Becoming an air traffic controller takes years of intense training, and only the top few percent of applicants are admitted to the education in the first place. Even the fact that you have to ask this question makes it seem like you have a very poor understanding of air traffic control.
The issue of not wanting people to land on a private airstrip has nothing to do with air traffic control. Air traffic controllers do not exist to tell pilots what they can and can't do - they are there to provide a service to the pilots! As others have pointed out, this would be a matter of trespassing. Pilots are very well aware that private airfields are just that - private. No one will just randomly spot a private airfield from the air and decide to land there without having first done some research - unless in emergency situations, of course.

+1 for "the fact you're asking this question at all means you should not even try it" regardless of whether you technically could. Which is not true anyway.

Have you checked your facts on the years of intense training, because as far as the FAA is concerned ANYONE can act as a controller at a NFCT.  Of course their AC on the topic suggests that the controller have a CTO certificate, and I think that is a good idea.  But the fact is that there are just very few regulations which impact the operation of a NFCT.  Perhaps you have a few authoritative cites which support your strong statements?

@mongo As a trainee air traffic controller in Europe, I have no idea what most of those acronyms mean. My answer covers a general point of view, not rules specific to individual countries, since there was no country specified in the original answer.

@J. Hougaard Congratulations on being an ATC trainee. From my perspective your answer sounds rather emphatic, while it is stated generally, clearly in the US and in Canada there are mechanisms for doing what the OP stated that they wanted to accomplish. There may indeed be similar ways in other countries. Apparently you have commented generally without a general check. If you read my answer NFCT is defined, and AC mentioned (Advisory Circular). That leaves CTO, which is someone who holds a Control Tower Operators' certificate. And just in case, FAA is in the US the Federal Aviation Admin...

"Pilots are very well aware that private airfields are just that - private. No one will just randomly spot a private airfield from the air and decide to land there without having first done some research" -- oopsie!

Without a control tower, the field would be "uncontrolled" in the eyes of the FAA, so no, you couldn't issue clearances per se. The FAA would probably take a dim view of an untrained individual playing air traffic controller at his private field.
That said, the field would still be private property, and you'd be within your rights to bar anyone whom you didn't invite from landing there. "No tresspassing", etc.  I don't think very many pilots assume that they can just land at any private airstrip they see -- emergency situations notwithstanding.
As a practical matter, even if you built yourself a platform & got a radio, those whom you hadn't invited would probably have no way to know what frequency to select, in order to be told not to land there. I don't think private strips get UNICOM or CTAF frequencies published on the charts, mainly since the traffic at such fields is presumed to be very, very low.

Private strips in the US are most certainly eligible for CTAF and UNICOM use, as well as for licensing of the ground station. A default frequency that could be used is 122.9 MHz.

private strips do have a plate in the regional document which lists the ATM contact information. Part of the approval of the flight plan is contacting the destination airport to verify that the airport is accepting traffic. These are separate from the inflight clearances provided by regional control stations which the OP would not be able to issue. The airstrip operator would be able to control flight operations at their site when they are open. A lot of paperwork needs to be tracked to do so though. its not just plugging in a radio.

Private fields do have a CTAF frequency - MULTICOM on 122.9. Anytime a field doesn't have a tower, FSS, or UNICOM frequency then 122.9 is the default CTAF frequency. (See AIM 4-1-9(g).)

There is also AFIS (aerodrome flight information service, callsign Info) and Radio type stations. These are not control towers and operators are not air traffic controlers. They provide advisory services and information, they do not control air trafic.
It is much more easy to get one of these stations to a small airport and its ATZ - aerodrome traffic zone. The people providing this service are indeed often owners or members of the club owning the airport.
They can tell the pilots if the runway is free for takeoff or landing, but they do not issue clearances you for that. They tell the pilots about other traffic in the circuit, in the ATZ and its intentions.  To some extent you can this way get to similar activity as tower ATCOs, but your instructions are nor clearances, they are advisories.
AFIS is a little bit more involved.  For example in Czech Republic most small airports had AFIS but almost all of them were converted to Radio which has fewer requirements because the common European regulations for AFIS and AFISO (AFIS officers) became more strict.
An airport can be controled in certain hours and uncontroled with just an AFIS at other times (LKLK).

This doesn't really answer the question

I'm sorry for voting to close this post as it is an interesting information.

I agree with the above comments. The information is interesting, but it does not address the question of issuing clearances. An abbreviated version of could make a good comment.

I'm not an expert but the information seems relevant to me, as in offering a different solution.

@Vladimir F, AFIS sounds similar to CTAF in the US, which is a common traffic advisory frequency.  It may be the tower frequency, and continues to function as a CTAF when the tower is not operating. It can also be a UNICOM frequency at a non-towered airport.  (I believe that technically AFIS or FIS is the equivalent of UNICOM.)  BTW, at least in the US, more than one UNICOM can be licensed at one airport. A company I worked for had their own UNICOM, at a towered field, and the two FBOs used another UNICOM. The FBO UNICOM frequencies were the ones published, and the company UNICOM was unpub.

The FAA has thousands of locations listed that are uncontrolled private fields. Some offer services, some don't, and some don't even have safe landing strips any longer.
They all have an ATM, and probably at the time of the submission had everything required for being a non FAA controlled Airport. The requirements have likely increased over time. (I've contacted the FAA about strips where the ATM has died and was told they don't have the manpower to check the small airstrips.)
You would in conjunction with the local ATS be able to approve and issue landing clearances for your airstrip. That is why an airstrip plate has the Airport Manager and Phone number listed.


text:
Are there big differences between Douglas Commercial 3 and Douglas Commercial 4?
I always thought of the DC-4 as a DC-3 with two added engines and somewhat improved hydros.
What are the actual differences between them?

Err, what is a 'hydro'?

Hydr"oaulics because "hydros" stuck to my mind because of NFSU2
NFSU2 Vet here

The DC-4 was a totally new design in all respects, as can be seen from the planform diagrams (wiki)

The DC-4 was larger, and structurally totally different:

Straight tapered wing (no sweepback)
Straight tubular fuselage, not the aerodynamic teardrop shape
Round fuselage cross-section. The original DC-4E was going to have a pressurised cabin. The later DC-4A did not implement this but retained the circular cross section necessary for pressurisation.
MTOW = 33,100 kg for the DC-4, 11,430 kg for the DC-3
Four engines of 1,081 kW each, while DC-3 had 2 engines of 890 kW each.
Tricycle landing gear instead of a tail dragger, as @Gerry points out.

All in all a larger aircraft, designed from scratch, implementing more modern features of a later age.

And tricycle gear instead of the conventional gear.

What did straight tapered wing added to the design ?

@JonathanIrons Better stall behaviour. Wing sweep is an evil that is necessary for high speed cruise, much higher than the cruise speed of the DC-4. The DC-3 had it implemented because the CoG turned out to be further aft than initially calculated

Also where did you get that image from ?
As I can see there isn't a site named planform diagrams (wiki)

The poor stall characteristics of the DC-3 were caused by the high taper of the wing and, consequently, highly loaded outer wings. Stall was worse with power on because the prop slipstream stabilized the inner wing. Stall was worse again with flaps down because that increased the loading of the outer wing. Sweep had little influence. See here for a 1937 documentary

@JonathanIrons The planforms are from the wikipedia articles about DC-3 and DC-4, they are a way down in the articles next to the specifications. I put them side by side scaled to wing span.


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Are Crew Resource Management (CRM) and other Human Factors methods effective?
I help in giving human factor training in both the start up phase and in the biennial continuous training. I am a bit tired of my students...especially those in aviation long term, being disillusioned in this subject. I have tried to find statistics or information where I can show that sitting the human factor training has in fact helped in the prevention of accidents and incidents in the maintenance environment. But have been unsuccessful in finding this information. Wondering if anyone knows where I could find this? Thanking you in advance. :)

I think it would be easier to find examples of where a lack of focus on human factors has led to incidents or accidents. An example of this that comes to my mind is British Airways 5390.

@aCVn A good example; however it doesn’t of course answer the question whether the continuation training provides any benefit over a single initial training.

@CptReynolds It also doesn't provide any information or statistics relating to its preventing accidents. Hence a comment; hopefully useful, but not an answer to the question OP asked.

@aCVn Of course. It’s a perfect example!

I'm not aware of any formal studies (though they might exist). Korean Air (KE) however is often used as an example of the improvement in safety to be had from good CRM. Back in the day, after a number of fatal crashes, KE employed an American pilot to put in CRM - with a focus on 'status' of captains, and the cultural barriers for F/O's to tell the CA that something was wrong. I'm pretty sure I read an article in Air Transport World at the time (years ago) that backed up KE's improvement in safety with better CRM.

If the question is whether repeating the same training every two years provides a benefit, especially for something people are (in theory) practicing every day, I'm not convinced it does. I zone out during repeat training. If you want people to see value (and pay attention), show them something new each time, preferably about how CRM saved people in a recent incident.

Yes StephenS, agree with you. have had a class now that say exactly the same thing... they zone out. But not running the courese and not paying attention is not going to solve it either. Thats why I was hoping to see stats on how things have improved since running the training. We have this figure of 80%of maintenance errors are caused by HF, so how come we cant find how "its changed" in the last 20-30 years.

A student of mine, who has a background in industrial engineering and is an emergency medicine physician, has morphed his career to include the application of CRM into emergency medicine and operating room procedures.  The health industry has in general been moving that way because it is saving lives and lawsuits.
Several people have published retrospective analysis of aviation accidents, which tend to contrast the kinds of errors which occurred prior to CRM, and the changes in flight deck politics.
Military team operations, firefighting and other industry segments have started incorporating CRM into their training, and with measurable result.
Much of CRM today was developed  in response to significant aircraft disasters in the 1970's coupled with research at NASA and some universities which provided more insight as to how crews work together.  As an example, the unquestioned authority of the senior captain, was a factor in an alarming number of major accidents.  That protocol has been substantially replaced with a more collaborative protocol, and there are fewer accidents involving the same aspects of flight crew dynamics.
The medical application paper referenced below probably has statistics and material you might find particularly useful in your training.
Journal Articles:
https://www.tandfonline.com/doi/abs/10.1207/s15327108ijap0104_3
A medical application reference which talks about lessons learned in aviation:
https://www.emsreference.com/printpdf/47
A scholarly critical data driven analysis:
https://apps.dtic.mil/dtic/tr/fulltext/u2/a502230.pdf

Technological advances continue to attempt to improve reliability and safety in
  aviation. Design considerations throughout the acquisition process must also continue to
  expound on integrating humans, including our cognitive and physiological capabilities, as
  fundamental aspects of aviation systems. Nevertheless, CRM training continues to be the
  primary method in mitigating the number of mishaps due to human crew coordination
  error in aviation. The program must go beyond simple training requirements and become
  more in grained into the culture. Perhaps the evidence found in this study suggests a
  transformation of cultural acceptance is gradually occurring.

Thank you mongo for that. Very informative. Alot of reading, and will definitely read it for inspiration. I appreciate you taking the time :)

Good explanation @mongo. Look up Korean Air and CRM (google Korean Air and CRM) for an example like the one you describe: cultural barriers between Captains and FOs were behind a number of crashes, until KE hired an American safety expert to help them implement good CRM, with a corresponding decrease in accidents. This case history is well-understood in the commercial airline industry, and the google search will refer you to some good information, if not papers.

Thanks Pete, I agree, it IS a good example. But only thing is that there was an extreme view to start with... I have students where this kinda of behaviour is worlds apart.  They are used to a flatter structure, so understanding the need for CRM training in these situations are beneficial and needed. It would be nice to see some concrete figures.. like in the figure that 80 of Aircraft maintenance errors are human factors... but thats from the 2000's so thinking now its almost 20 years of practicing HF training, so would be good to see that now its down to 60% for example.. to show its helping

@Maria, please consider that CRM and HF practices have been in place long before FAA and other agency popularization.  For example, go back to the checklists read by the non-flying pilot or flight engineer during WWII.  Those were designed to have a team work together to reduce risk.  The institution of CRM was not one event, rather it is a continuum.  Clearly, though, after notable crashes in the 70's there was more emphasis on the ability of any crew member to challenge another, and that aspect marks a notable change in CRM approaches.

Good point Mongo :)

Your problem is probably because you are searching for data using the term "human factors" when you should use the term "Crew Resource Management", which is the aviation term for it.  Here is a pretty good Flight Safety.org PP presentation that may work for your purposes.

It is called “human factors” when training ground staff e.g. MRO personnel. I can vouch for it being a tad repetitive when the same 4+ hrs CBT is run through every two years or so.

Thank you for your replies. Thats a good point John, will research using Crew Resource Managment. And Cpt Reynolds you are correct when it is for MRO personnel. I fell at this stage I need hard facts to show that the repetitive training does actually mean something. We dont have this on CBT and think its a great advantage and wish to keep it that way.

Of course CRM isn't the sole reason for the improvement in safety.  In my opinion the other really major factor is the introduction of the 2D moving navigational map made possible by TV tube displays (glass cockpit).   The reduction in mental workload was absolutely massive because suddenly you didn't have to maintain a mental image of your situation based on indications from dials.  But CRM has had a broadly holistic effect on operational safety in general.


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How does scaling of UAV size impact range?
Lets say you have two autonomous small aircraft, one with a wingspan of 200 cm and one with 400 cm. Both have the same general design. They are both optimized for travel distance on one full tank (gas tank size, engine size, optimum speed, etc). Which one has greater range?
In other words, does it help to be large or small if you want to make a travel distance record?

If you compare geometrically similar aircraft, the larger one will have more range.
First, its volume grows by the third power while areas grow only with the square of its scale, so wing loading will be higher for the larger aircraft. This will translate into a higher cruise speed, because the range optimum dictates an optimum speed for each aircraft. In a first order approximation, an aircraft of twice the size will fly at 1.41 times the speed of a smaller aircraft. The much higher internal volume will allow it to carry much more fuel, but even when the fuel fraction for both designs is kept constant will the larger aircraft fly farther.
If we restrict fuel to the same fraction of total mass, the exponent for mass increase is slightly above 2. All surfaces grow by an exponent of 2, but the stresses would be higher in a linearly scaled structure, so the structure of the larger aircraft needs no be beefier. An exponent between 2.2 and 2.3 has been found to best represent reality. This means that doubling dimensions will result in a mass increase by a factor of 4.76. In order to fly at the same polar point, the large aircraft needs to fly at 109% of the speed of the small aircraft.
In a more detailed analysis, we need to first look at the installed power: If we focus on piston engines and scale the engine in the way we scale the aircraft, for a size increase by a factor of two will the displacement grow by a factor of eight while the engine speed will decline by a bit less than a factor of two. The smaller engine will have higher friction, thermal, sealing and combustion losses, so it will have a noticeably lower efficiency. If we just look at statistical data, power output grows slightly less than linearly with displacement:

Statistical data for power over displacement. Source: Menon, S., and Christopher P. Cadou. "Scaling of Miniature Piston-Engine Performance, Part 1: Overall Engine Performance." Journal of Propulsion and Power 29.4 (2013): 774-787
Next, we need to look at Reynolds number effects. The larger aircraft will fly at a higher Reynolds number for two reasons: Increased length and increased speed. Together, a doubling in length will translate into a first-order Reynolds number increase by a factor of 2.18. The coefficient of friction will scale with Re$^{-0.3}$, so doubling the length of an airplane will reduce the friction coefficient of the large airplane to 79% of that of the small airplane. This will not only affect total drag, but also the polar point for best range. Since the optimum lift coefficient is proportional to the square root of zero-lift drag, the optimum lift coefficient for the large airplane will only be 89% of that of the half-size airplane and cruise speed will be higher by a factor of 1.225. This means that dynamic pressure is higher by a factor of 1.5.
Ideally, this calculation needs to be iterated, but for now I keep it at one iteration step.
This higher dynamic pressure now needs to be multiplied by the increase in reference area to arrive at the zero-lift drag: 1.5 times 4 times 0.79 means that doubling the size will let zero-lift drag grow only by a factor of 4.74. Since zero-lift and induced drag are of the same size at the optimum cruise point, the same factor applies to the total drag. The required power, however, is proportional to speed, so doubling the size will increase the power demand by a factor of 5.78. This is well below the power increase from a scaled-up engine, so the larger aircraft actually needs a proportionally smaller and lighter engine, leaving more reserves for fuel. Or it can scale up the engine linearly and load proportionally more fuel.
Fuel consumption is proportional to engine power, but we get another advantage from the larger engine: Its specific fuel consumption will be slightly better:

Specific fuel consumption over displacement (same source as figure above).
In sum, the larger aircraft will

cruise at 122.5% of the speed of the small aircraft
will consume 5.5 times as much fuel per time for a mass increase by a factor of 4.76. Combined with the speed increase this leaves only a 5.5% advantage.
If we assume a scaled-up engine with an increased power by a factor of 7.27, the mass increase can be by a factor of 6 with maybe twice the fuel fraction of the smaller aircraft and 7 times higher fuel flow per time. This takes into account that the cruise speed will grow with aircraft mass.

This 70% longer flying time coupled with the then 24% higher cruise speed will leave the smaller aircraft in the dust.

Thanks Peter for an excellent and detailed answer! I also found the research paper you cited, and it is a very interesting read.

Thanks! Scaling effects are indeed interesting ..  and as honorable mentions, there is the "Spirit of Butt's Farm" https://en.wikipedia.org/wiki/The_Spirit_of_Butts%27_Farm, a model airplane of 5kg crossing the atlantic from NewFoundLand to Ireland in 38 hours, at roughly half the speed of Alcock and Brown (in 1919).

All else being equal, a larger span will provide an advantage in the form of less induced drag.
That being said, in the real world one cannot arbitrarily increase span without paying a weight penalty, in this case because more structural weight will be required to support the larger bending moment of that span, so whether going from $200cm$ to $400cm$ will be worth it is unclear without the rest of the numbers.
As for your subquestion, it helps to be large enough to carry your powerplant and energy storage systems, which don't scale in the same manner as the airframe and thus impose an initial design requirement. If you review some of the range or endurance record-setting designs, you will see they have one theme in common: they are built around their powerplants, with little weight and space devoted to other systems.

"built around their powerplants" ... and their fuel tanks!

Endurance and range of an aircraft has nothing to do with physical size, but rather with performance, fuel consumption and fuel capacity (assuming calm winds). One problem with assuming that scaling up will give you more range is that you also have to get bigger engines as part of the upscaling, and additional fuel consumption may negate any other advantage of scale, such as larger fuel tanks.

Thanks Juan. Yea this is the reason I asked. There are many factors that affect range, and you list a few. But before starting to optimize the fuel tank, engine size/tuning, etc, it helps to know whether there is an inherit advantage of having an aircraft small or large. When doubling the size, some things scale to the power of two (airfoil lift area), while others scale to the power of three (weight for example). Maybe this is too complicated to give an answer to, and only practical tests can tell.

Your assumption of scale translating to performance might be correct when it comes to gliders, for example, but powered aircraft are a different story. Scale of an airframe vs scale of its other non-airframe components is a different story. :)

One factor in scale that is yet to be quantified is drag penalty from pitch oscillation.  This is why glider designs (and birds) have retained their horizontal stabilizers. Unless an aircraft has a very sophisticated computer sensor (these always work perfectly, right?) and control system, the H stab remains a vital part of pitch control.
Mass also plays a role in minimizing pitch oscillations caused by wind turbulence.  Heavier means slower acceleration  a = F/m in response to a gust.  Similar the increased comfort of driving a very heavy truck down a bumpy road compared with a light car.  Increased mass to surface area ratio of the larger aircraft acts as a more efficient damper of wind effects.
These factors, along with the Reynolds drag reduction Peter mentioned, work in favor of the larger aircraft.
But do not stop at 200 to 400 cm scale comparison.  Take it all the way up to the Convair B-36.  Before air to air refueling become practical and commonplace, these intercontinental giants were unmatched in range and endurance.


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Is there any FAR defining an "introductory" or "familiarization" flight?
I have given a number of young people their first inspirational flight. I am a CFI, but I do not issue any endorsement for these flights, and do not charge for my time or the aircraft. Is there any FAR defining "introductory" or "familiarization" flight, or addressing how many times a non-flight-student (no student pilot medical certificate and no student pilot log book) can receive an introductory or familiarization flight?

Free aircraft/instructor??? You are one of very few that offer that, usually introductory/discovery flights run $100 or more. It is also a way to filter out people just wanting airplane rides versus those who are seriously considering training. If you want to offer free flights, I'd suggest joining the Young Eagles program, but you should charge for your airplane at the very least for intro/discovery flights. I'd be interested in hearing about your conversion rate...

There's no formal definition or regulation that I could find; introductory flights aren't defined in 14 CFR 1.1, for example. I'm not sure why the FAA would care how often you fly with someone, or what the difference is between an introductory flight and any other flight with a non-paying, 'non-logging' passenger.
The only other people who might care about it are the TSA but if you aren't providing instruction during the flight then that shouldn't matter either. Introductory flights are usually understood to be a "demonstration flight for marketing purposes" (49 CFR 1552.1) and therefore exempt from TSA requirements, but there doesn't seem to be any rule about how many demo flights you can make with an individual.

The verbal direction we have received from the TSA is that the marketing rule is only for the first flight. Yeah, yeah..."but show me the reg," right? Given the aggressor here will be the TSA and admin courts typically side with the administrative org, take your chances with multiple "intro rides" at your own risk. I sincerely belive the spirit of the rule is pretty clear and I rarely take a pro-regulation (or even regulation tolerant) position on anything.

@acpilot That's a good point, and it's a messy situation for sure. Did the TSA tell you that their intro flight direction applies to foreigners only, or also to US citizens? At least for now citizens don't need any TSA approval anyway until they solo.

I don't know the details.  I was not part of the talk.  Management was.

@acpilot OK, thanks. I was wondering because I've read about the 'one flight' statement from the TSA before, and it always seems to be a verbal thing and always in the context of foreign students. But all the references I can find were written before the TSA started vetting citizens too, so I don't know if their 'guidance' has changed now.

There is no FAR regarding intro flights for prospective student pilots. Different instructors handle things differently.
I use a log sheet which was created with a spreadsheet program, which I use for student flights. It has critique blocks for different parts of the lesson, which includes preflight, engine start, take-off, medium bank turns, etc.  You get it.
The prospective student gets graded same as if they were a continuing student.  I sign the sheet, and they do as well, and they get the original and I keep a copy.  Their time is dual-received and mine is dual-given. They get the same post-flight briefing I give students, and it includes tips on handling parts of the flight, perhaps motion induced feelings, and what to expect in future lessons. I tell them  to keep the sheet, and should they take up lessons in the future, that sheet can become an entry in their logbook, and put into an envelope in the rear of the logbook.
This way students have a better idea how lessons will work, and the same importance is given to the first lesson as will be the case in all subsequent lessons.  It is situational, but usually my intro flights take the same 90 minute time that I plan for other training flights.
I always try to have the student practice a few things they do well at, such as power settings, trim or medium bank turns to a heading, so that there are parts of their critique which will show higher scores. The scores are genuine, and if the student does poorly, that is the critique they get, along with any coaching.
Through the years I have given initial rides to 75 yo and 9 yo. These rides are lessons, and not "Eagle Flights" or some other ride.  Accordingly, I handle the TSA required documentation as if the flight initiated flight lessons.


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What is Temperture of VSI and limits of accurate value?
Within a temperature range of +50C and -20C the VSI is Accurate to within limits of :

A)+- 200 ft/min
B)+- 0 ft/min
c)+- 75 ft/min
D)+- 300 ft/min

At what ROC or ROD?  For example, the VSI is extremely accurate with no altitude change, but the error may increase with high ROC or ROD.  So more information is needed, unless one wants to assume a VSI of +/- 2000 fpm or something like that.

Also, to be accurate, is your measurement outside the lag error of the VSI?

It was a quastion in CPL exam of my country  in answer sheet the " A" is answer but i dont know why .

So you know the correct answer, but you want to know why...  Well, the simple explanation is that is the accuracy limitations of that pressure based gauge.  Every system has tolerances, that is the tolerance of that system.
In one of the airplanes I flew we had an digital instantaneous VSI that could be read from a display, and it came from a GPS coupled ring laser gyro INS.  It was too jumpy to be useful, but on a stable descent it was nice to be able to cross check it against the pressure VSI.
They were usually pretty close, but there was always some slight difference.  Assuming that the instantaneous VSI was more accurate, (it would also have some tolerance...) then that difference would be the accuracy limit of the gauge.


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Can I use the autoland mode if the airport is unknown to the FMC database?
Can I use the autoland if I have to land on an airport which is not known to my FMC database? Is it possible to insert the coordinates to get the autoland mode?

I have my fingers crossed that you're talking in the context of a simulation.

Dinosaur that I am, I can't help but point out that back in the 1990s we had autoland, but we had no FMC, and there was no way to enter coordinates to the autoland. All it required was a functioning ILS, both localizer and glideslope.

@Terry, it still does. Never heard of an autoland requiring coordinates to land. GPS approaches still have a 300’ minima, so technology is still far out for RNAV autolands

@Radu094 It will continue that way even for GPS. GLS downloads the GPS corrections and approach path coordinates, which can include segments and curves, over the data link radio. The crew selects the right path to use encoded in the channel number.

@IanF1 yes, it's just for theoretical knowledge. No operation purpose.

Autoland is an autopilot mode.
AUTOLAND could be « armed » while the autopilot is receiving FMS inputs, but once it is « active » it doesn’t use FMS data but the ILS receivers or the ILS and GPS receivers.
No need of the FMS neither for the approach, nor for AUTOLAND

Right now the only technology to perform a full autoland relies on ILS (and in increasingly rare cases MLS), and then only when the airport and plane allow CAT III operations.  Since ILS relies only on radio navigation based at the airport, no GPS coordinates are required.  ILS approaches are quite handy if for some reason you are working with an unfamiliar or unreliable GPS or FMS.
However, there are several practical reasons why autoland at an airport that's not in the FMC might be more difficult, besides being highly unusual.  If you're used to LNAV and VNAV, those obviously won't guide you to the approach. Similarly, not having RNAV or LPV available can be inconvenient if the airport isn't using low-visibility procedures for ILS CAT III and you have to land using some other procedure. Finally, CAT III landings have a number of disadvantages listed here like increased pilot workload and higher operational requirements.


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Has this USAF flight violated russian airspace?
Just encountered this interesting flight on FlightRadar24:

From the path, it looks like it may have "violated", or let's say, been to, russian airspace. Even if not, one has to wonder what kind of mission was performed up there.
If it is a spy mission, I would expect the flight to keep the transponder turned off for a longer time?
So, main question is: Is this track inside russian airspace? Bonus question: Any idea what kind of mission takes you up there?
EDIT: Clarification: I do not mean the landmass the aircraft is visibly flying over. That is Norway, I know :-) I meant the proximity to russian islands and the "vector" where transponder info is starting at - but yes, all outside the 12-mile-zone, as I now learnt.

OpenStreetMap shows national waters/airspace boundaries (12 NM) as magenta lines.

Was this a round-trip track starting and ending at the location of the red airplane icon for JAKE17? Or is this showing the end of the track in Norway and the beginning of the track off the big island on the right?

@JBH The crew seems to have turned on the transponder only where the line starts (or maybe that's where the FR24 coverage starts), and they were still in the air at the time of the screenshot and going southwards. Tracked them for a while (as they were heading roughly in my direction :-)), but not sure at which airbase they eventually landed.

Do not mix the exclusive economical zone (EEZ, 200 NM) and the sovereign area. The aircraft has been in the EEZ, not in the sovereign area (12 NM) of the Russian Federation.
EEZ
Yes the aircraft crossed the border of the Russian Federation EEZ. The EEZ extends up to 200 NM from the coastline (even further if there is a continental shelf continuity; Russian Federation tried to use this possibility to extend its EEZ up to the Svalbard archipelago, but it's now resolved).

Surce: Wikmedia.
However the airspace over the EEZ is not a sovereign airspace, in fact its entirely free for aircraft.
Sovereign airspace definition
Sovereignty over airspace is limited to 12 NM from the coastline according to Chicago and UNCLOS conventions. UNCLOS defines the limit of the territorial seas, and the Chicago convention states the airspace over territorial seas is sovereign:

Source: ICAO.
Obviously the flight path is not close to this limit at any time.
ADIZ, need to be identified
Unlike the US, the Russian Federation has no official air defense identification zones (the ADIZ concept, which is not part of any international treaty). It means overflying aircraft have no obligation to identify themselves unless they want to enter the sovereign airspace.
EEZ vs sovereign airspace confusion
The EEZ defines important economic rights for activities from the sea surface. However UNCLOS does not grant any right on the airspace over the EEZ (art. 57, 58 and 78). In particular the EEZ adds no restriction for overflying, aircraft are granted all of the rights defined for high sea areas (the seas beyond the EEZ). E.g.:

In the exclusive economic zone, all States, whether coastal or
land-locked, enjoy, subject to the relevant provisions of this Convention, the freedoms referred to in article 87 of navigation and overflight and of the laying of submarine cables and pipelines, and other internationally lawful uses of the sea [...]

This confusion seems to be pervasive in the media which often report the "violation" of Taiwanese airspace by China, while these flights are entirely lawful in the EEZ (ignoring the ADIZ which is another topic) as long as the 12 NM national airspace is respected (assuming Taiwan is sovereign, which is indeed disputed).

Are you possibly thinking that the landmass that the aircraft is flying over is Russian territory? It is actually flying over Norway. In the image below I colored in green the border between Russia and Norway, and in red the border between Russia and Finland.

The closest that it got to Russian landmass appears to be about 28 nautical miles (32 miles, 52 km). As mentioned in another answer to your question the limit is 12 nautical miles. And as mentioned in a comment by @Bianfable, OpenStreetMap shows this boundary.

As I love Norway, I am very well aware of that country's borders ;-) But yes, I massively overestimated the 12-mile-zone size, and did not think about checking with OpenStreetMap.

Given the scale, that is far outside the 12 mile limit.
What mission? RC-135W Rivet Joint is for monitoring electronic traffic.
https://www.af.mil/About-Us/Fact-Sheets/Display/Article/104608/rc-135vw-rivet-joint/
From Wikipedia:
"Stated objectives include broadcasting a clear signal that the US, and thus NATO, is aware of Russian movements in the area of operations."
https://en.wikipedia.org/wiki/Boeing_RC-135
And regarding the "awareness", we can frequently see on FR24 other ISR platforms over eastern Poland and Romania. Rivet Joint, JSTARS, AWACS.  Tankers to keep them fueled. As well as Global Hawk doing laps over the Black Sea.
What we don't see are all the fighters up there with them. F-15/16/22/35/Typhoon/Eurofighter.

Yep, I also frequently see the aircrafts in the mentioned areas, but well, this is a little bit off course here, isn't it? This is why I was also wondering about the mission profile.

This is not the first time I've seen -135RWs up there, on a similar path.